Word: without
(lookup in dictionary)
(lookup stats)
Dates: during 1990-1999
Sort By: most recent first
(reverse)
...year. The hardheaded Elsa got that upped to $16,000.) Though occupied with his lonely struggle to unify gravity and electromagnetism in a single mathematical framework, he watched Germany's saber rattling with alarm. Despite his earlier pacifism, he spoke in favor of military action against Hitler. Without fanfare, he helped scores of Jewish refugees get into an unwelcoming U.S., including a young photographer named Philippe Halsman, who would take the most famous picture of him (reproduced on the cover of this issue...
With the help of his friend Marcel Grossmann, Einstein studied the theory of curved spaces and surfaces that had been developed by Bernhard Riemann as a piece of abstract mathematics, without any thought that it would be relevant to the real world. In 1913, Einstein and Grossmann wrote a paper in which they put forward the idea that what we think of as gravitational forces are just an expression of the fact that space-time is curved. However, because of a mistake by Einstein (who was quite human and fallible), they weren't able to find the equations that related...
...theory of curved space-time was called general relativity to distinguish it from the original theory without gravity, which was now known as special relativity. It was confirmed in spectacular fashion in 1919, when a British expedition to West Africa observed a slight shift in the position of stars near the sun during an eclipse. Their light, as Einstein had predicted, was bent as it passed the sun. Here was direct evidence that space and time are warped, the greatest change in our perception of the arena in which we live since Euclid wrote his Elements about...
...extremely fine scales, space-time, and thus reality itself, becomes grainy and discontinuous, like a badly overmagnified newspaper photograph. The equations of general relativity simply can't handle such a situation, where the laws of cause and effect break down and particles jump from point A to point B without going through the space in between. In such a world, you can only calculate what will probably happen next--which is just what quantum theory is designed...
Nature rarely bestows gifts on scientists, however, without exacting a price, and the price, in this case, takes the form of additional complications. Among other things, string theory requires the existence of up to seven dimensions in addition to the by now familiar four (height, width, length and time). It also requires the existence of an entirely new class of subatomic particles, known as supersymmetric particles, or "sparticles." Moreover, there isn't just one string theory but five. Although scientists could rule out none of them, it seemed impossible that all of them could be right...